Spark plug



May 19, 1925- A. CHAMPION SPARK PLUG Filed March 8, 1920 T 'bwve'm rm U4, @r DP Q 1 Mo 1 440 L Patented May 19, 1925.

UNITED STATES 1,538,870 PATENT OFFICE.

ALBERT CHAMPION, 0F FLINT, MICHIGAN, ASSIGNOR TO A C SPARK PLUG COMPANY,

OF FLINT, MICHIGAN, A CORPORATION OF MICHIGAN. v

SPARK PLUG.

Application filed March 8, 1920. Serial No. 364,015.

specification.

My invention relates to spark plugs of the general class or type whereina series of sparks are caused to pass between an outer electrode whichis supported by the hollow metallic shell or casing of the plug,

and an inner electrode which extends through an insulating membersecured in place within said outer shell or casing; and particularly tocertain features associated with the outer of the said electrodes, thatis the one which is carried by and projects from the inner end of theexternal hollow metallic shell or casing of the plug.

The principal object of my invention is.

to rovide an improved form, construction, and arrangement of the outerelectrode of a spark plug of the general class or type above referred toand by the use of which improvements a more rlgid and a stronger outerelectrode is secured; and at the same time to provide a plug in whichthe life thereof is prolonged, because of a distribution of the sparkswhich are produced when the plug is in use throughout a greater ortionof the extremities of the inner an of the fixed outer electrodes thanhas heretofore commonly been the case.

With the above and other objects of invention in view, my inventionconsists in the improved fixed or outer electrode construction andarrangement illustrated in the accompanying drawing and hereinafterdeform of spark plug equipped with one form of my improved electrode,the view being partly in section and partly in side elevation.

Figure 2 is a sectional view showing the inner end of the spark plugshown in F ig ure 1 upon a larger scale, the outer electrode beingsomewhat modified as to certain of its features.

Figure 3 is a view similar to Figures 1 and 2, but showing a slightlydifferent form of my invention.

F igure l is a view showing the inner end of a plug having an electrodemade in accordance with my invention, and in which the same differssomewhat from the form shown in the other figures.

Figure 5 is a fragmentary view illustrat ing the form of electrode shownin Figure 2 upon a larger scale, and in perspective, to show thearrangement of the base thereof relative to the portion of the outercasing from which it projects.

Figures 6 to 10, inclusive, are fragmentary views illustrating variousmodifications of my improved outer electrode, particularly as regardsthe form or shape of the free end thereof.

Referring now to the drawing, the reference numeral 10 designates theexternal'hollow metallic shell or casing of a spark plug of common andwell known form, and within which an insulating member 11 is secured inany of the ways at present employed in securing insulating members inplace within .such shells or casings; while the reference numeral 12designates the inner electrode of the plug, the same being supported ina central position within a passage formed in and extendinglongitudinally of the said insulating member.

Carried by and extending from the inner end of the metallic shell orcasing 10 is an outer electrode designated by the reference numeral 13,one end of which is welded or otherwise secured to the end of the saidshell or casing. This outer electrode is ob long, or substantiallyrectangular, in cross section, and the inner end or base thereof issecured to the inner end of the shell or casing in any way, as bywelding the same to said inner end as above stated and in accordancewith the patent to A. Schmidt, No. 1,319,423, October 21, 1919. Thearrangement of the said outer electrode is shown as lot) such that itsbase portion where it is welded to the free end of the shell or casinghas its longer dimension extending circumferentially of the said innerend; so that the greatest dimension of the joint between said electrodeand the surface of the shell from which it projects extends at rightangles to the diameter of said shell;

The free end of the outer electrode 13, to which the reference numeral14 is applied, is bent over toward the central electrode atsubstantially a right angle to the body portion of said outer electrode,and the length of said bent over portion is such that its extremity liesadjacent the central electrode 12 of the finished plug, so that sparksmay pass betewen the electrodes when the plug is in use.

Various of the advantages of my invention will be secured by the use ofan outer electrode extending from the inner end of the shell or casingof the plug and the end of which is bent over so as to lie adjacent theinner electrode and the cross section of which outer electrode issubstantially .rectangular, as above'pointed out. I prefer, however, totwist the bent over portion 14 of the said outer electrode throughout anangle of substantially ninety degrees, so as to cause the extremitythereof to extend substantially parallel with the end portion of thecentral electrode adjacent which it lies. Such a construction andarrangement of the outer electrode results in a distribution of thesparks which pass between the extremities of the electrodes throughout amuch greater area than would be the case if the outer electrode wascircular in cross section; thus distributing the wear due to the passageof the sparksbetween the two electrodes throughout a much greater areathan would otherwise be the case and prolonging the life of the plug.

The extremity of the outer electrode may if desired be provided with apluralit of sparking points or teeth, as indicate by the referencenumerals 15, which construction provides a plurality of points betweenwhich the spark pass and a plug in which the sparks passing between thecentral electrode and the outer electrode will pass between variouspoints ofsaid electrodes; each spark occurring between the centralelectrode and some one point of the outer electrode, the particularpoints between which the spark passes being determined in the case ofeach discharge by the resistanceof the path along whichthe currentflows. It therefore follows that as soon as the resistance of the pathalong which sparks are assumedto be passing becomes greater than theresistance of another path the sparks will cease to pass between thefirst assumed points, and will pass between another point of the outerelectrode and the central electrode; thus distributing the wear due tothe passage of the sparks between all the points upon the outerelectrode, or along the entire length thereof if the extremity of saidelectrode is not provided with distinct teeth and providing an electrodestructure in which the life of the outer electorde is very muchincreased.

It will furthermore be appreciated that my invention provides anelectrode of uniform cross section throughout, and one which may beformed from w1re of oblong or rectangular cross section as hereinbeforeexplained; and which electrode when twisted so as to provide a sparkingedge extending parallel with the inner electrode results in a plug inwhich the sparks are distributed throughout a much greater area thanwould otherwise ordinarily be the case; such end being attained, as willbe appreciated, with- I out imparting any special shape to theextremity' of the outer electrode as the distribution of the sparks"throughout the entire area thereof will occur even if the toothedconstruction at the end be not employed. At the same time the outerelectrode is of greater strength because of the form of the wireemployed in the formation thereof and the arrangement of the weldedjoint between its fixed end and the end of the external shell or casing;and the twisting of the same intermediate its length provides anextremely rigid form of electrode and one in which the change in angularposition between the two parts thereof at the right angle at which thetwist occurs imparts increased strength and rigidity to the electrode atthe bend thereof, which has heretofore been a weak point in spark plugelectrodes of the right angular type, that is of the type wherein thefree end of the electrode is bent over at a right angle to the bodyportion thereof to cause its extremity to lie close to the centralelectrode of the plug.

The use of wire oblong in cross section in the formation of the outerelectrode in addition to providing strength and rigidity thereinprovides an electrode of increased mass through which a free flow ofheat may occur from the spark gap where heat is pro-. duced by thepassage of the sparks along and through said electrode and to theexternal casing of the plug, and from there to the engine, thusproviding for the conduction of the heat produced at the spark gap awaytherefrom more effectively than would be the case if an electrode ofless cross sectional area was employed and maintaining a comparativelylow temperature at the spark gap, while at the same time retaining theadvantages of an outer electrode separate from the shell or casing ofthe plug and projecting from the innerend thereof.

The advantages of enhanced strength and stiffness and of increased massfor providing a more free flow of heat from the sparking points inherentin an outer electrode which is oblong in cross section as disclosedherein are secured irrespective of the form of the extremity thereof atwhich the sparks pass from said electrode to the inner electrode; fromwhich it follows that the extremit-y of the said outer electrode ma bevariously shaped without departing rom my invention regarded in itsbroader aspect, and as comprehending an outer electrode which is oblongin cross section. Thus in the form of my invention illustrated in Figure1 the extremity of the stationary electrode is straight, while inFigures 2,.3, 4 and 5 it is serrated,a distribution of the sparksthroughout the area of the extremity being however secured in bothcases; while in the form illustrated in'Figure 6 there are two surfaces16 arranged at about a right angle to one another and in between whichsurfaces the inner electrode 17 is 10- cated, thus securing adistribution of the sparks between the central electrode and the twosurfaces in question.

In the form of electrode illustrated in Figures 7 and 8 the end of theelectrode is tapered, as indicatedat 18 and '19, thus'reducing the areaat the extremity thereof as is permissible in the case of an electrodemade from analloy which wears away slowly at the sparking pointswithout, however,

7. reducing the strength or stiffness of the electrode as a whole whichis imparted to it by its oblong cross sectional area and withoutreducing the efiiciency thereof as regards the conduction of heat awayfrom the sparking point and to the shell of the plug; While Flgure 9 shos a form of electrode in which the end2 thereof is widened, thusproviding an edge of greater length than the width of the electrode anda more extended surface along or over which the. sparks may bedistributed as hereinbeforeexplained; such edge being either serrated asshown, or smooth ifsuch form is deemed desirable.

Figure 10 shows a form of my invention in which the outer electrode 21while still oblong in cross section is secured in place to the outershell 22 of the plug with its longer dimension radial, relative to thecen- Letters Patent tral electrode; the base of the said outer electrodebeing either welded to the flat end 'tral electrode.

tion thereof, and t sparking points or teeth.

carried by said shell and projectingfrom the inner end thereof, and thearrangement of which electrode is such that its longer dimension extendscircumferentially of the end of said shell or casing; .and a centralelectrode supported by an insulating member secured in place within saidshell; the free end of said outer electrode being bent substantially atright angles to the fixed portion thereof, and twisted through an angleof substantially ninety degrees, and

the/extremity of which outer-electrode extends substantially parallelwith and lies adjacent the said central electrode and is provided withaplurality of sparking points or teeth. I

2. In a spark-plug of the class described, an external hollow metallicshell or casing; an outer electrode oblong in cross section 1 carried bysaid shell and projecting from the. inner endthereof, and thearrangement of whlch electrode is such that its longer dimension extendscircumferentially of said shell or casing; and a central electrode sup--ported by an insulating member secured in place within said shell; thefree end of said,- outer electrode being bent substantially at rightangles to'the fixed portion thereof, and twisted through an angle ofsubsta-ntially ninety degrees, and the extremity of which outerelectrodeextends substantially parallel with and lies 3. In a spark plug oftheclass described, an external hollow metallic shell or casing; anouter electrode oblong in cross section carried by said shell andprojecting fromthe inner end thereof, and the arrangement of whichelectrode is such that its longer dimension. extends circumferentiallyof the end of said shell or casing; and a central electrode supported byan insulating ber secured in place within said shell; the

free end of said outer electrode being bent j substantially at rightangles to the fixed pore extremity'of said outer electrode lyingadjacent said .central elecadjacent the said cenj trode and beingprovidedwith aplurality of I 4. In a spark plu of the class-described,

an external hollow s ell or casing; an outer electrode oblong in crosssection carried by said shell and projecting from the innerend thereof;and a central electrode supported by an insulating'member secured inplace AL ERT CHAMPION,

